Application programs (hereunder may be simply referred to as “app(s)”) for performing text chats in which users exchange their text messages via terminal devices such as smartphones have been provided (for example, see Patent Literature 1). In the text chats using such an app, two or more users form a group and when members of the group input text messages for the chat group, the messages are sequentially shown in chronological order on the terminal device of each user who belongs to the chat group (each member of the chat group).